Cathode ray storage tube using a dark trace layer and a phosphor layer



Sept. 8, 1964 N. F. FYLER 3,148,281

cATRonE RAY sToRAGE TUBE USINGA DARK TRACE LAYER ANDA REosRHoR LAYER Filed Feb. 28. 1961 nrw-l 3,148,281 CATHODE RAY STORAGE TUBE USlNG A DARK TRACE LAYER AND A PHSPHOR LAYER Norman F. Evier, Menlo Park, Calif., assigner to Litton Precision Products, inc., a corporation of Delaware Filed Feb. 28, i961, Ser. No. 92,306 3 Claims. (Cl. Z50- 217) This invention relates to storage tubes of the cathode ray tube type.

Many forms of digital information storage have been proposed heretofore. They include magnetic cores and tapes and also various forms of cathode ray tubes. The cathode ray tube storage devices are particularly useful in providing high speed random access storage. A collateral advantage provided by some cathode ray tube storage devices is visible storage and read-out. The present invention involves an improvement and simplication of cathode ray storage tubes of this type.

in accordance with the present invention, a cathode ray tube screen is provided with three successive layers including a transparent resistive layer, a layer of dark trace material, and a conventional layer of phosphor. Dark trace material is a substance which will become opaque when bombarded with electrons. The application of heat to dark trace material restores the material to its normal transparent condition. In practice, the layers are applied successively to the faceplate of a cathode ray tube, with the transparent resistive material being preferably located against the faceplate, and the successive additional layers of dark trace and phosphor materials being superposed on the transparent resistive material.

In operation, the electron beam is initially employed to store digital information in selected discreet areas in a raster on the dark trace material. This is accomplished by increasing the energization level of the electron beam so that it will penetrate the phosphor layer and render selected areas of the dark trace material opaque. Following the storage of information in the dark trace material, the information may be read-out at will by applying the electron beam at reduced voltage or current levels to the same selected areas on the face of the cathode ray tube. The low energy electron beam Will illuminate the phosphor material which is behind the dark trace material. If the dark trace material in front of the energized phosphor area has been previously rendered opaque, the light from the phosphor material will not pass through the faceplate; however, if the dark trace material is still in the transparent condition, light will pass through the faceplate and energize a light sensitive element such as a photocell or phototransistor.

The storage pattern which has been impressed on the dark trace material may be removed by the application of current to the transparent resistive layer which is ad jacent the dark trace material. When this resistive material is heated up, the pattern on the dark trace material is removed and a new storage pattern may be entered.

The storage tube in accordance with the present invention, has the advantages of simplicity and ease of constructure, as well as ease of utilization. It also provides a visible indication of the information which is currently stored in the cathode ray tube. It is primarily adapted for semi-permanent storage requirements wherein the stored data is only changed at periodic intervals.

The novel features Which are believed to be characteristic of the invention, both as to its organization and method of construction and operation, together with further objects and advantages thereof, Will be better understood from the following description considered in connection With the accompanying drawing in which an illustrave embodiment of the invention is disclosed, by way of example. It is to be expressly understood, however, that 3,l48,28l Patented Sept. 8, 1964 the drawing is for the purpose of illustration and description only and does not dene limitations of the invention.

In the drawing:

FIG. 1 shows a cathode ray storage tube and associated circuitry in accordance with the invention; and

FIG. 2 is a detailed cross-sectional view of a portion of the faceplate of the tube shown in FIG. 1.

Referring to the drawing, FIG. 1 shows a cathode ray tube 12, a digital data processing circuit 14, and an optical system including a photo-sensitive element 16 and a lens 18 for sensing signals which appear on the screen ofthe tube l2. The tube 12 includes the faceplate 20, suitable deflection arrangements 22, and a neck 24 in which the electron gun structure is mounted. Within the tube 12 on the inner surface of the faceplate Ztl are three layers of different materials. Starting from the faceplate these layers 26 include a layer of transparent resistive material, a layer of dark trace material, and a layer of phosphor.

With regard to materials, the transparent resistive material may, for example, be of stannous oxide. Other known transparent resistive materials may also be employed. The dark trace material may be any of a number of materials which are known to become opaque upon the application of an electron beam of suitable intensity. One such material is potassium chloride. Materials of this type are discussed at page 664 of a text entitled Cathode Ray Tube Displays by T. Soller, M. A. Starr, and G. E. Valley, Ir., M.I.T. Radiation Laboratary Series, Volume 22, McGraw-Hill Book Company, Inc., 1948, New York. The phosphor layer may be any of a number of known commercially available phosphors which produce light at an energization level Which is less than that required for providing a dark trace on the intermediate layer.

With regard to the operation of the system, shown schematically in FIG. l, the resistive material immediately adjacent the faceplate 20 may be initially energized to clear all data from the layer of dark trace material. This may be accomplished by applying suicient current on leads 28 to heat the dark trace material to a temperature at which it becomes transparent. This temperature may, for example, be approximately 50 C. for a typical dark trace material. After the stored information has been cleared by the heating step mentioned above and the tube faceplate has cooled down, information may be stored by the application of a high energy beam to the layers on the faceplate 20. This high energy beam is in contrast to the lower energy beam to be discussed below which merely energizes the phosphor material and does not affect the state of the dark trace material. The energy level of the beam may be controlled either by changing the anode voltage or by varying the current level of the beam. Thus, for example, the high energy beam could involve 10 kilovolt electrons while the lower er1- ergy beam for energizing the phosphor layer could operate at a 5 kilovolt level. Using a constant high voltage beam, the energy level may be changed by varying the current of the beam. Typical high and low current levels are 10 microamperes and one-tenth microampere, respectively.

When the writing cycle is initiated, signals are applied on leads 3@ to the power supply 32 for the cathode ray tube. This serves to switch the electron beam to its high energization state, either by changing the grid or the anode voltage. The beam is turned off and on as signals applied on leads 34 control the sweeping of the electron beam across the raster on the cathode ray tube faceplate. Following the completion of the writing cycle, selected areas of the dark trace material have been rendered opaque.

To more clearly indicate the nature of the storage phenomenon of the present invention, reference is made to FIG. 2 of the drawing. In FIG. 2 the transparent resistive material 36 is shown in a layer against the glass faceplate 20 of the cathode ray tube. The successive additional layers 38 and 40 of dark trace and phosphor materials, respectively, are superposed on the resistive layer 36.

A typical storage pattern is shown in the diagram of FIG. 2. Thus, two areas 42 and 44 have been rendered opaque by the application of a high intensity electron beam. lIn the diagram of FIG. 2 a low intensity or reading electron beam is applied to area 46 of the phosphor material 40. The resultant light which is generated in the phosphor material 46 cannot pass through the opaque area 42, which is preferably somewhat larger than the zone 46. Accordingly, no light passes through the optical system to be received by the photosensitive device i6, as shown in FIG. l. If the area 42 had not been rendered opaque by the previous storage of information, light from the phosphor area 46 would have been transmitted through Ithe storage area 42 toward the optical system in the manner indicated by arrow 48 in FIG. 2.

Y To indicate conditions under which light would be transmitted through the dark trace material, reference is made to the storage area 50 between the storage areas 42 and 44. This area is transparent, as it Was not energized by a high intensity electron beam during the Write cycle of the data processing apparatus. Accordingly, if an electron beam were applied to the zone 52 on the phosphor layer as indicated schematically by arrow 54, the resultant light would be transmitted directly through the layer 38 of dark trace material toward the optical system. The presence of darkened material in a particular area 42, 44 or 50 therefore represents one binary signal, and the absence of darkening in the designated discrete areas of layer 38 represents the other binary signal.

For completeness, certain other details should be discussed. Thus, for example, deflection apparatus 22 may be in the form of coils providing magnetic deflection, or plates, which would normally be within the tube, for providing electrostatic deflection. The optical system, including lens 18 and photocell 16, may be replaced by a photoconductive layer on the outer surface of cathode ray tube 20 with thin conducting films on either side ofY the photoconductive layer. Light from the phosphor material 40 which is not shadowed by darkened areas in layer 38 would then cause conduction in the photoconductive layer and close the circuit between the two conductive lms.

While the operation of digital data process circuitry is well known to persons skilled in the art, it may be desirable to mention an example of the mode of operation of such circuits. During the Write cycle, a number may be stored in a certain series of areas in layer 38. This is accomplished by deflecting the high intensity beam to a predetermined series of areas in layer 38. Thus, for example, the successive areas 42, 50 and 54 in FIG. 2 could represent the binary number 101, where the digit l is represented by the darkening of an area in layer 38 by the high intensity beam, and where the binary digit is represented by a transparent or translucent area. Subsequently, during the read cycle, the electron beam would be deflected to lthe same series of areas. When the W intensity beam strikes area 46, no output signal would be observed through the optical system. When it strikes the phosphor screen in front of area S0, the optical system would ysense an output signal; and then, when the electron beam is directed onto the phosphor screen in front of area 44, the optical system would not receive an output signal. Thus, the presence of an output signal to the optical system would represent the binary digit 0, and the absence of a signal would represent the binary number 1. Thu-s, as the read electron beam impinges successively upon points on the phosphor screen behind the area 42, Sti and 44, in succession, the binary number 101 would be read out.

It is to be understood that the above-described arrangements are illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention. Typical alternative arrangements have been mentioned above in the course of the detailed description. Accordingly, it is to be understood that the present invention is to be limited only by the spirit and scope of the appended claims.

What is claimed is:

l. In combination, a cathode ray tube having a faceplate, successive layers of Va dark trace material and a phosphor mounted within and generally parallel to said faceplate, with the dark trace material closer to the faceplate means for directing an electron beam onto said layers, means for changing the energy level of said electron beam, means for heating said dark trace material to render it transparent, photosensitive electrical arrangements in front of said faceplate for detecting urrshadowed light from said phosphor layer, and a digital data processing system for supplying storage and scanning signals to said cathode ray tube and for receiving output signals from said photosensitive arrangements.

2. In a dark trace storage tube:

a cathode ray tube having a faceplate,

successive layers of a dark trace material and a phosphor mounted within said tube and generally parallel to said faceplatel with the dark trace material located closer to the faceplate,

means for directing an electron beam onto said layers to darken selected areas of said dark trace material,

means for directing an electron beam toward the inner surface of said layers to energize the phosphor material so that light is visible through the faceplate in areas where said dark trace material has not been darkened, and

photosensitive electrical arrangements for detecting unshadowed light from said phosphor layer.

, 3. ln an information storage system:

a cathode ray tube having a faceplate, successive layers of a dark trace material and a phosphor having relatively short persistency mounted within and generally parallel to said faceplate with the dark trace located closer to the faceplate,

means for entering digital data into said tube by the scanning of a high intensity electron beam to darken selected areas of said dark trace material,

means for reading out information from said tube by scanning a lower intensity electron beam across said phosphor material, and

means including a photosensitive pickup device for receiving radiant energy from selected areas of said phosphor layer which are not shaded by darkened areas of the intervening dark trace layer.

References Cited in the tile of this patent UNITED STATES PATENTS 2,755,404 Levy July 17, 1956 2,836,753 Hodowanec May 27, 1958 2,950,409 Berthold et al. Aug. 23, 1960 

1. IN COMBINATION, A CATHODE RAY TUBE HAVING A FACEPLATE, SUCCESSIVE LAYERS OF A DARK TRACE MATERIAL AND A PHOSPHOR MOUNTED WITHIN AND GENERALLY PARALLEL TO SAID FACEPLATE, WITH THE DARK TRACE MATERIAL CLOSER TO THE FACEPLATE MEANS FOR DIRECTING AN ELECTRON BEAM ONTO SAID LAYERS, MEANS FOR CHANGING THE ENERGY LEVEL OF SAID ELECTRON BEAM, MEANS FOR HEATING SAID DARK TRACE MATERIAL TO RENDER IT TRANSPARENT, PHOTOSENSITIVE ELECTRICAL ARRANGEMENTS IN FRONT OF SAID FACEPLATE FOR DETECTING UNSHADOWED LIGHT FROM SAID PHOSPHOR LAYER, AND A DIGITAL DATA PROCESSING SYSTEM FOR SUPPLYING STORAGE AND SCANNING SIGNALS TO SAID CATHODE RAY TUBE AND FOR RECEIVING OUTPUT SIGNALS FROM SAID PHOTOSENSITIVE ARRANGEMENTS. 